1. Field of the Invention
The invention relates to a magnetic transducer, a thin film magnetic head using the same, a method of manufacturing a magnetic transducer and a method of manufacturing a thin film magnetic head. More particularly, the invention relates to a magnetic transducer capable of obtaining the more excellent rate of resistance change, a thin film magnetic head and a method of manufacturing the same.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk or the like. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a magnetoresistive effect (hereinafter referred to as an MR element) that is one of magnetic transducers and a recording head having an inductive-type magnetic transducer, is widely used as the thin film magnetic head.
MR elements include an AMR element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), a GMR element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect), and so on.
The reproducing head using the AMR element is called an AMR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as the reproducing head whose surface recording density exceeds 1 gigabit per square inch, and the GMR head is used as the reproducing head whose surface recording density exceeds 3 gigabits per square inch.
As the GMR film, a xe2x80x9cmultilayered type (antiferromagnetic type)xe2x80x9d film, an xe2x80x9cinductive ferromagnetic typexe2x80x9d film, a xe2x80x9cgranular typexe2x80x9d film, a xe2x80x9cspin valve typexe2x80x9d film and the like are proposed. Of these types of films, the spin valve type GMR film is considered to have a relatively simple structure, to exhibit a great change in resistance even under a low magnetic field and to be suitable for mass production.
FIG. 19 shows the structure of a general spin valve type GMR film (hereinafter referred to as a spin valve film). A surface indicated by reference symbol S in the drawing corresponds to the surface facing a magnetic recording medium. This spin valve film has the stacked structure comprising an underlying layer 91, a soft magnetic layer 92 made of a soft magnetic material, a nonmagnetic layer 94 made of a nonmagnetic material, a ferromagnetic layer 95 made of a ferromagnetic material, an antiferromagnetic layer 96 made of an antiferromagnetic material and a protective layer 97, the layers 92, 94, 95, 96 and 97 being stacked in this order on the underlying layer 91. Exchange coupling occurs on an interface between the ferromagnetic layer 95 and the antiferromagnetic layer 96, and thus the orientation of magnetization Mp of the ferromagnetic layer 95 is fixed in a fixed direction. On the other hand, the orientation of magnetization Mf of the soft magnetic layer 92 is freely changed in accordance with an external magnetic field.
A direct current is fed through the ferromagnetic layer 95, the nonmagnetic layer 94 and the soft magnetic layer 92 in the direction of a biasing magnetic field Hb, for example. However, this current is subjected to the resistance in accordance with a relative angle between the orientation of the magnetization Mf of the soft magnetic layer 92 and the orientation of the magnetization Mp of the ferromagnetic layer 95. Receiving a signal magnetic field causes the change in the orientation of the magnetization Mf of the soft magnetic layer 92 and thus the change in electrical resistance of the spin valve film. This change in the resistance is detected as the change in a voltage. Recently, it has been desired that this rate of resistance change (sometimes referred to as a rate of MR change) be made higher in order to allow magnetic recording at ultra-high density exceeding 20 gigabits per square inch.
A cited reference xe2x80x9cCoFe specular spin valves with a nano oxide layerxe2x80x9d, 1999 Digests of INTERMAG 99, published by May 18, 1999 reports that the rate of resistance change has been improved by providing an oxide layer called an NOL layer for the ferromagnetic layer of the spin valve film.
However, there is no description about the material and film thickness of the oxide layer called the NOL layer in the above-mentioned cited reference. Moreover, it is not clear where the NOL layer is formed in the ferromagnetic layer. Furthermore, a relationship between the rate of resistance change and any properties other than the rate of resistance change is not obvious.
More particularly, the above-described known cited reference has a problem that precision of repeatability is deteriorated because a coercive force of the soft magnetic layer is 14 (Oe: oersted), which is greater than 3 (Oe) that is an acceptable limit of the coercive force of a general spin valve film.
The invention is designed to overcome the foregoing problems. It is an object of the invention to provide a magnetic transducer which can increase a rate of resistance change and can obtain good values of other properties, a thin film magnetic head, a method of manufacturing a magnetic transducer and a method of manufacturing a thin film magnetic head.
A magnetic transducer of the invention including a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer comprises a soft magnetic interlayer formed in the soft magnetic layer and having magnetism and electrical resistance higher than the electrical resistance of the soft magnetic layer.
In a magnetic transducer of the invention, the soft magnetic interlayer having the resistance higher than that of the soft magnetic layer exists in the soft magnetic layer. Thus, when a sense current flows through the magnetic transducer, the soft magnetic interlayer reflects electrons and thus limits a route for the electrons. As a result, the rate of resistance change is increased, and therefore even a low signal magnetic field can be detected. Moreover, the soft magnetic interlayer has the magnetism. Thus, the respective magnetizations of two portions in the soft magnetic layer facing each other across the soft magnetic interlayer are integrally changed together in accordance with an external magnetic field such as the signal magnetic field. Thus, a coercive force of the soft magnetic layer can be reduced, and therefore a small variation in output and a high precision of repeatability can be obtained. Moreover, thermal stability is high. This causes less deterioration in properties even if a manufacturing process includes a process of heat treatment. The above advantages permit magnetic recording at high density exceeding 20 gigabits per square inch, for example.
A magnetic transducer of the invention can further adopt the following modes in addition to the above-described constitution.
That is, it is desirable that 0.3Tnxe2x89xa6D1 less than Tn, where Tn represents a thickness of the soft magnetic layer and D1 represents a distance between the nonmagnetic layer and the soft magnetic interlayer. Moreover, the distance D1 between the nonmagnetic layer and the soft magnetic interlayer may be 1 nm or more and less than 8 nm. Thus, a range of movement of the electrons is not excessively narrowed but can be effectively limited. Consequently, the higher rate of resistance change can be obtained.
Furthermore, it is desirable that the soft magnetic layer has a first soft magnetic layer containing at least Ni in a group consisting of Ni (nickel), Co (cobalt), Fe (iron), Ta (tantalum), Cr (chromium), Rh (rhodium), Mo (molybdenum) and Nb (niobium), and a second soft magnetic layer containing at least Co in a group consisting of Ni, Co and Fe. In this case, it is desirable that the soft magnetic interlayer is formed in the first soft magnetic layer. The soft magnetic interlayer is thus formed in the first soft magnetic layer, whereby the coercive force can be further reduced.
Additionally, it is desirable that the soft magnetic interlayer contains at least one of oxide, nitride and nitride oxide. Thus, the soft magnetic interlayer can be magnetically stabilized, and therefore the variation in output can be reduced.
Moreover, it is desirable that the thickness of the soft magnetic interlayer is from 0.5 nm to 1.0 nm inclusive. Thus, the route for the electrons can be effectively limited, and therefore the higher rate of resistance change can be obtained.
Additionally, a ferromagnetic interlayer having the magnetism and the electrical resistance higher than the electrical resistance of the ferromagnetic layer may be formed in the ferromagnetic layer. In such a configuration, when the sense current flows through the magnetic transducer, the route for the electrons is further limited by the soft magnetic interlayer in the soft magnetic layer and the ferromagnetic interlayer in the ferromagnetic layer. As a consequence, the rate of resistance change is further increased. In this case, it is desirable that 0.2Tkxe2x89xa6D2xe2x89xa68Tk, where Tk represents the thickness of the ferromagnetic layer and D2 represents the distance between the nonmagnetic layer and the ferromagnetic interlayer. Moreover, the distance D2 between the nonmagnetic layer and the ferromagnetic interlayer may be from 0.6 nm to 3.6 nm inclusive. Thus, the rate of resistance change can be increased, and an exchange coupling magnetic field between the antiferromagnetic layer and the ferromagnetic layer can be sufficiently increased. Moreover, the thermal stability is high. This causes less deterioration in properties even if the manufacturing process includes the step of heat treatment. Accordingly, the high rate of resistance change can be obtained.
Another magnetic transducer of the invention including a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer comprises a ferromagnetic interlayer formed in the ferromagnetic layer and having magnetism and electrical resistance higher than the electrical resistance of the ferromagnetic layer, wherein 0.2Tkxe2x89xa6D2xe2x89xa60.8Tk, where Tk represents the thickness of the ferromagnetic layer and D2 represents the distance between the nonmagnetic layer and the ferromagnetic interlayer.
Still another magnetic transducer of the invention including a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer comprises a ferromagnetic interlayer formed in the ferromagnetic layer and having magnetism and electrical resistance higher than the electrical resistance of the ferromagnetic layer, wherein the distance between the nonmagnetic layer and the ferromagnetic interlayer is from 0.6 nm to 3.6 nm inclusive.
In another magnetic transducer and still another magnetic transducer of the invention, when the sense current flows through the magnetic transducer, the electrons are reflected by the ferromagnetic interlayer formed in the ferromagnetic layer and thus the route for the electrons is limited. As a result, the rate of resistance change is increased. Moreover, the ferromagnetic interlayer has the magnetism. Thus, the respective magnetizations of two portions in the ferromagnetic layer facing each other across the ferromagnetic interlayer are fixed together by exchange coupling between the ferromagnetic layer and the antiferromagnetic layer. Consequently, the rate of resistance change can be increased, and the exchange coupling magnetic field between the antiferromagnetic layer and the ferromagnetic layer can be sufficiently increased. Moreover, the thermal stability is high. Thus, the effect that even if the manufacturing process includes the step of heat treatment, less deterioration in properties occurs and thus the high rate of resistance change can be obtained is achieved.
Another magnetic transducer and still another magnetic transducer of the invention can further adopt the following modes in addition to the above-described configuration.
That is, it is desirable that the ferromagnetic interlayer contains at least one of oxide, nitride and nitride oxide. Thus, the soft magnetic interlayer can be magnetically stabilized, and therefore the variation in output can be reduced. Moreover, it is desirable that the thickness of the ferromagnetic interlayer is from 0.5 nm to 1.0 nm inclusive. Thus, the route for the electrons can be effectively limited, and therefore the higher rate of resistance change can be obtained.
A thin film magnetic head of the invention comprises a magnetic transducer of the invention.
A method of manufacturing a magnetic transducer of the invention is a method of manufacturing a magnetic transducer including a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer. The method comprises the step of forming a soft magnetic interlayer having higher electrical resistance than the soft magnetic layer and magnetism, in the soft magnetic layer.
In a method of manufacturing a magnetic transducer of the invention, the magnetic transducer having the high rate of resistance change, the low coercive force and the excellent thermal stability can be easily manufactured.
A method of manufacturing a magnetic transducer of the invention can further adopt the following modes in addition to the above-described configuration.
That is, it is desirable that the soft magnetic interlayer is formed by partly oxidizing, nitriding or oxidizing and nitriding the soft magnetic layer. Thus, the good soft magnetic interlayer can be easily obtained.
Another method of manufacturing a magnetic transducer of the invention is a method of manufacturing a magnetic transducer including a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer. The method comprises the step of forming a ferromagnetic interlayer having higher electrical resistance than the ferromagnetic layer and magnetism in the ferromagnetic layer, wherein the ferromagnetic interlayer is formed at such a position that 0.2Tkxe2x89xa6D2xe2x89xa60.8Tk holds, where Tk represents the thickness of the ferromagnetic layer and D2 represents the distance between the nonmagnetic layer and the ferromagnetic interlayer.
Still another method of manufacturing a magnetic transducer of the invention is a method of manufacturing a magnetic transducer including a nonmagnetic layer having a pair of facing surfaces, a soft magnetic layer formed on one surface of the nonmagnetic layer, a ferromagnetic layer formed on the other surface of the nonmagnetic layer and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the nonmagnetic layer. The method comprises the step of forming a ferromagnetic interlayer having higher electrical resistance than the ferromagnetic layer and magnetism in the ferromagnetic layer, wherein the ferromagnetic interlayer is formed at such a position that the distance between the nonmagnetic layer and the ferromagnetic interlayer is from 0.6 nm to 3.6 nm inclusive.
In another method of manufacturing a magnetic transducer and still another method of manufacturing a magnetic transducer of the invention, the magnetic transducer having the high rate of resistance change and being excellent in thermal stability or the like can be easily manufactured.
The method of manufacturing a magnetic transducer of the invention can further adopt the following modes in addition to the above-described configuration.
That is, it is desirable that the ferromagnetic interlayer is formed by partly oxidizing, nitriding or oxidizing and nitriding the ferromagnetic layer. Thus, the good ferromagnetic interlayer can be easily obtained.
A method of manufacturing a thin film magnetic head of the invention uses a method of manufacturing a magnetic transducer of the invention in the step of forming the magnetic transducer.